Working with Copado User Stories, you might see how the autonumber field on the User Story object is being increased automatically. Apparently, the User Story number does not follow the order but jumps to a higher one without reason.

The root cause for this is a Salesforce standard behavior, prioritizing safety before sequential autonumbers, as pointed in the following article: https://help.salesforce.com/articleView?id=000327616&type=1&mode=1